package/python-gnupg: bump to version 0.5.1

For change log, see:
https://github.com/vsajip/python-gnupg/releases/tag/0.5.1

This commit also adds a comment about the archive being checked with the
PGP signature published by the package author.

Signed-off-by: Julien Olivain <ju.o@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/python-gnupg/python-gnupg.hash

@@ -1,5 +1,8 @@
 # md5, sha256 from https://pypi.org/pypi/python-gnupg/json
-md5  19cc1aef3a612b7b5f13e388260e65d4  python-gnupg-0.5.0.tar.gz
-sha256  70758e387fc0e0c4badbcb394f61acbe68b34970a8fed7e0f7c89469fe17912a  python-gnupg-0.5.0.tar.gz
+# also checked PGP signature from:
+# https://bitbucket.org/vinay.sajip/python-gnupg/downloads/python-gnupg-0.5.1.tar.gz.asc
+# with key: 9147B477339A9B86
+md5  c5d99c5f0456f8cbf69324ec5e6acaff  python-gnupg-0.5.1.tar.gz
+sha256  5674bad4e93876c0b0d3197e314d7f942d39018bf31e2b833f6788a6813c3fb8  python-gnupg-0.5.1.tar.gz
 # Locally computed sha256 checksums
 sha256  4104ca980dbca7603fc553078378eb14566a76f819d033d7bff89fd6a97e181b  LICENSE.txt

package/python-gnupg/python-gnupg.mk

@@ -4,8 +4,8 @@
 #
 ################################################################################
 
-PYTHON_GNUPG_VERSION = 0.5.0
-PYTHON_GNUPG_SITE = https://files.pythonhosted.org/packages/e3/5c/5ff9877001616912a74f4377cd5f80925b31a678087800beae5b28bdb80e
+PYTHON_GNUPG_VERSION = 0.5.1
+PYTHON_GNUPG_SITE = https://files.pythonhosted.org/packages/98/62/7737485f44bd4d7d904f4094372f4119195865b29f119fa51a98e121a13a
 PYTHON_GNUPG_LICENSE = BSD-3-Clause
 PYTHON_GNUPG_LICENSE_FILES = LICENSE.txt
 PYTHON_GNUPG_CPE_ID_VENDOR = python